Authe is located some 45 km east by south-east of Rethel and 20 km north-east of Vouziers. Access to the commune is by road D12 from Brieulles-sur-Bar in the north which passes through the centre of the commune and the village and continues south to join the D947 south of the commune. The commune consists entirely of farmland.[3]
The Bar river forms the south-western border of the commune as it flows north-west to follow the Canal des Ardennes to join the Meuse near Vrigne-Meuse. The Ruisseau de Saint-Pierremont flows from the north-east of the commune past the village and joins the Bar on the south-western border of the commune.[3]